Horst-Michael Ludwig's research while affiliated with Bauhaus-Universität Weimar and other places
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Publications (122)
The pathway of nucleation and growth of C-S-H is important for understanding the hydration kinetics of Portland cement and subject of the present work. Therefore, analytical ultracentrifugation (AUC) is used to characterize the nucleation of C-S-H in aqueous environments with a detection capability ranging from ions to sub-micron particles. Complem...
In this paper, we propose a model based on surface reactions and ion transport to capture the development of C-S-H not only at early age but also at later age of hydration. With the assumption of the mass balance between dissolution and precipitation processes, we derive an equation for the C-S-H precipitation rate. The model takes both the coverag...
Researchers, Institutions and Companies investigating, testing, and implementing ways to massively reduce the CO2 emissions of the building industry. Depending on the country, carbon neutrality wants to be achieved within the next 20-25 years. However, a central approach to reduce the carbon footprint of concrete is decreasing the clinker content o...
Cement suspensions are subject to hydration processes causing dissolution of cement clinker, precipitation of hydration products and changes in the ion content of the carrier liquid. These mechanisms take place in parallel and control the workability of cement suspensions. The precipitation of nano-granular ettringite is currently believed to be on...
Citation: Kraft BIE, Müller M, Achenbach R, Ludwig HM, Raupach M. 2023. Influence of CO2 Concentration During Accelerated Carbonation Tests with Alternative Binders. NanoWorld J 9(S2): S195-S200. Abstract One approach to improve the carbon footprint of concrete is the use of alternative binders, which can be produced with less CO 2 (Carbon dioxide)...
The substitution of Portland cement clinker with a combination of limestone, calcined clays and set regulator (calcium sulphates) is a promising way to reduce CO2 emissions of concrete. These cements are described as Limestone Calcined Clay Cement (LC3, https://lc3.ch/). Calcined clays are known to have a high specific surface area, which results i...
The demands on modern building materials are constantly increasing. Innovativesolutions produce a multitude of binders and concretes that often have a verycomplex, multiscale heterogeneous composition. Multi-scale imaging of structuralcharacteristics is still a challenge but will provide basic understanding of essentialmaterial properties.Over cent...
To accurately simulate the hydration process of cementitious materials, understanding the growth rate of C-S-H layers around clinker grains is crucial. Nonetheless, the thickness of the hydrate layer shows substantial variation around individual grains, depending on their surrounding. Consequently, it is not feasible to measure hydrate layers manua...
Coupling of microstructural and physico-chemical modelling of cement hydration is a key step towards prediction of material performance. In this paper, a physicochemical model based on surface reactions and ion transports is proposed to capture the development of calcium-silicate-hydrate (C-S-H) not only at an early age but also at later ages of hy...
Introduction: Metakaolin (MK) is used as supplementary cementitious material to reduce the CO 2 footprint of Portland cements. However, the early hydration of Portland cement (OPC) is often retarded due to its use. The present work investigates the mechanisms of this retardation. Focus is laid on the interaction of MK with the main clinker phase C...
The nucleation and growth of calcium–silicate–hydrate (C–S–H) is of fundamental importance for the strength development and durability of the concrete. However, the nucleation process of C–S–H is still not fully understood. The present work investigates how C–S–H nucleates by analyzing the aqueous phase of hydrating tricalcium silicate (C 3 S) by a...
In this paper, we introduce an Extended Finite Element Method (XFEM) to simulate the wave propagation in an imperfect concrete structure. The XFEM allows simulating a small discontinuity in the structure and the change of this discontinuity without re-meshing the whole structure. Therefore, the meshed structure is kept consistent while the structur...
To achieve the important goal of clinker reduction for concretes in cold and temperate climates, it is important to understand the underlying mechanisms for salt frost scaling. Two conflicting damage theories dominate the current State of the Art – the glue spall theory and the cryogenic suction theory. In this study, important aspects of both theo...
The freezing point of pore solution in concrete is lowered due to the action of surface forces in the porous network. During a salt frost attack the freezing point is further depressed by ingressing salt ions. The combination of both effects was studied by low temperature differential scanning calorimetry (LTDSC) on hardened cement paste. The resul...
The applications of steel slag (SS) in the cement industry provide a sustainable solution both for construction materials and industrial solid wastes, but the problem of easily bleeding presents a threat to its later performance and utilization efficiency. This work was designed to improve the water retention of SS blended cement by using hydroxyet...
This study combines 2D element mappings obtained by laser ablation with inductively coupled plasma mass spectrometry (LA-ICP-MS) and energy dispersive X-ray spectrometry (EDX) in the scanning electron microscope (SEM) to analyse the chemical composition of cement clinker phases. It is revealed that this approach enables to determine the major and t...
This study combines 2D element mappings obtained by laser ablation with inductively coupled plasma mass spectrometry (LA-ICP-MS) and energy dispersive X-ray spectrometry (EDX) in the scanning electron microscope (SEM) to analyse the chemical composition of cement clinker phases. It is revealed that this approach enables to determine the major and t...
Characterisation of cement clinkers is a prerequisite to optimise properties of cements and concretes. Therefore, the protocol to prepare and characterise cement clinkers using electron backscatter diffraction (EBSD) in combination with energy dispersive X-ray spectrometry (EDS) is described.
It is shown that argon broad ion beam polishing delivers...
The cement industry gains increasing public attention because of the high CO2 emissions for which it is accountable. One approach to improve the carbon footprint of cement production is the development of alternative binders, which can be produced with less energy consumption. These alternative binders have a reduced clinker to cement ratio or cont...
One major component of Portland cement clinker is Ca2SiO4 (C2S, belite). Synthetic samples of three polymorphs, β-C2S (larnite), γ-C2S (calcio olivine), and x-C2S were investigated by high-temperature oxide melt solution calorimetry at 700 °C to obtain their enthalpies of formation. A natural sample of wollastonite (CaSiO3) was measured for compari...
In this work cracks in concrete slices were measured by machine. Those slices are thinner than a human hair. Hollow spaces in those slices were filled up with a very liquid yellow resin. This highlights all the cracks. A microscope with a camera was used to make images of a whole slice. This created one complete and very detailed image of an area t...
This study demonstrates the application and combination of multiple imaging techniques (Light Microscopy, Micro X-ray Computer Tomography (μ-CT), Scanning Electron Microscopy (SEM) and Focussed Ion Beam - Nano Tomography (FIB-nT)) to the analysis of the microstructure of hydrated alite across multiple scales. However, by comparing findings with mer...
The process of ASR (Alkali-Silica Reaction) induced expansion and damage in pavement concrete specimens is investigated using laboratory experiments and computational modeling. In the experimental program, the concrete specimens are subject to CS-CPT (climate simulation concrete prism test) to obtain ASR induced expansion with and without external...
![Fig. 1 Binary H 2 O-NaCl phase diagram, calculated after [15],...](publication/354476740/figure/fig1/AS:1066185533698069@1631209848460/Binary-H-2-O-NaCl-phase-diagram-calculated-after-15-including-NaCl-solution_Q320.jpg)
Scaling of concrete due to salt frost attack is an important durability issue in moderate and cold climates. The actual damage mechanism is still not completely understood. Two recent damage theories—the glue spall theory and the cryogenic suction theory—offer plausible, but conflicting explanations for the salt frost scaling mechanism. The present...
Replacing part of calcium aluminate cement (CAC) with reactive rice husk ash (RHA) can directly reduce the impact of rice husk disposal on environment and lower the CO2 footprint of cement. RHA is comparable in chemical composition to silica fume, and thus has the potential to similarly improve the hydration of CAC. In the present study the develop...
The aim of this study is to explore the influence of HEMC with different total substitution degrees and polyacrylamide (PAAm) modification on the properties of steel slag cement mortar. The results show that HEMC increases the water retention rate, consistency, tensile bond strength, and flexibility of all types of steel slag cement mortars. The ad...
Vor dem Hintergrund der Klimadebatte werden zur Reduzierung des CO 2 ‐Austoßes vermehrt Alternativen zu Portlandzement als Bindemittel im Beton entwickelt. An diese alternativen Bindemittel werden die gleichen Ansprüche hinsichtlich ihrer Dauerhaftigkeit wie an Portlandzement gestellt. In der vorliegenden Studie wurden Mörtel mit Bindemittel aus de...
To obtain satisfying water retention and improved viscosity, cellulose ether (CE) has been widely used in fields such as tile adhesives, repair mortars and self-levelling mortars. But the impacts of CE on the hydration and microstructure of calcium sulfoaluminate (CSA) cements, especially on the hydration and water evolution are still missing some...
Surface chemistry of mineral phases in aqueous environments generates the electrostatic forces involved in particle-particle interactions. However, few models directly take into account the influence of surface speciation and changes in solution speciation when the diffuse layer potential profiles of approaching particles overlap and affect each ot...
This paper studies the influence of hydroxyethyl methyl cellulose (HEMC) on the properties of calcium sulfoaluminate (CSA) cement mortar. In order to explore the applicability of different HEMCs in CSA cement mortars, HEMCs with higher and lower molar substitution (MS)/degree of substitution (DS) and polyacrylamide (PAAm) modification were used. At...
Demonstration of the application of FIB/SEM on hydrated alite
Extrusion-based additive manufacturing (AM), or three-dimensional (3D) printing, has matured into a set of advanced methods to automate the construction of large-scale concrete structures, while minimizing cost and material waste. However, current AM data models are inadequate for 3D concrete printing due to insufficient incorporation of informatio...
Extrusion-based additive manufacturing (AM), or three-dimensional (3D) printing, has matured into a set of advanced methods to automate the construction of large-scale concrete structures, while minimizing cost and material waste. However, current AM data models are inadequate for 3D concrete printing due to insufficient incorporation of informatio...
Additive manufacturing (AM) of concrete structures, a technology to automate the architecture, engineering, and construction industry, has been gaining relevance over the past decade. Current data models employed for AM of concrete structures have been evolving slower than AM technologies, most of which relying on solutions that are not suitable fo...
In cold and moderate climates concrete can be subjected to a combined salt frost attack, which can cause scaling damage. Consequently, numerous test procedures were developed to determine the resistance of concrete compositions against this kind of attack. These tests typically mimic a severe attack with high levels of saturation, e.g. as for concr...
The rheological properties of fresh cement paste are highly influenced by a large number of parameters, among which the most important factors are the applied shear stress, and the shear history, the age of the sample and the temperature. The effects of these parameters on the yield stress (designated as structural limit stress in this work), the v...
An open question in predicting the rheological properties of cement suspensions has been whether changes of rheology during hydration are merely a result of shifts in the electrostatic interaction patterns of the particles over time, or whether and to which extent steric bridging by hydration products occurs. The latter could explain phenomena such...
Production of low-energy cements would result in energy saving and lower CO2 emissions related to reduced consumption of fuel and high-grade limestone as a raw material. Belite rich clinker, made more reactive by doping with combination of S and Li, could possibly be one of the low-energy alternatives for Portland cement clinker. Paper describes th...
The aim of this study is to investigate alkali silica reactivity of rice husk ash (RHA) in cement paste. Scanning electron microscope in combination with Energy-dispersive X-ray spectroscopy was used to analyse the mechanism of alkali silica reactivity of RHA. The results indicate that RHA has paradoxical effect on alkali silica reaction (ASR) in c...
Realistic modeling of the meso-structural development of concrete enables the prediction of material properties. The present study develops and deploys a computer model to simulate the growth and porosity of calcium silicate hydrate (C-S-H) phases. The growth kinetics is governed by a simplified function that can be related to dissolution and preci...
The use of dolomite powder as a supplementary cementitious material is gaining interest in the cement industry, e.g. to replace limestone powder in regions with limited access to high quality limestone. However, dolomite is not stable under alkaline conditions. Whether the resulting dedolomitizion is detrimental to durability of concrete has been d...
A recent groundbreaking approach to automate the construction process is the implementation of additive manufacturing (AM), i.e. three-dimensional (3D) printing, due to the development of printable concrete materials. Currently, AM is venturing in large-scale concrete construction with the development of large-scale 3D concrete printers, enabling t...
Currently there are two different models, the glue spall model and the cryogenic suction model, which have the potential to describe the mechanism for salt frost scaling correctly. The cryogenic suction model attributes scaling to the uptake of unfrozen, highly concentrated brine at sub-zero temperatures. Therefore, it cannot fully account for the...
Some thermodynamic properties of calcium aluminate monocarbonate hydrate (3CaO⋅Al2O3⋅CaCO3⋅10.7H2O), a typical hydration product of cement were determined in this study. This includes enthalpy ΔfH° = −8166.4 ± 7.7 kJ/mol, standard entropy S° = 652.4 ± 2.2 J/(mol⋅K) and heat capacity Cp° = 716.8 ± 3.6 J/(mol⋅K) at 298.15 K. The Gibbs free energy cal...
The objective of using supplementary cementitious materials (SCMs) in cement is to reduce costs and the overall CO2 output of the cement production. Against the background of an increasing demand for cement and a decreasing availability of common SCMs, calcined clays serve as alternative material for the industrial-scale manufacture of composite ce...
Wiederholte Frost‐Tau‐Wechsel können in Zusammenhang mit der Einwirkung von Feuchtigkeit und Tausalzen eine Schädigung der Betonoberfläche durch Abwitterungen verursachen. Der Frost‐Tausalz‐Widerstand von Beton wird momentan vorwiegend über deskriptive Ansätze gewährleistet, also indirekt über Vorgaben zur Betonzusammensetzung und Nachbehandlung. I...
The knowledge of the aqueous phase composition during the hydration of tricalcium silicate (C3S) is a key issue for the understanding of cement hydration. A new in‐situ method of computing calcium ion concentration from the measurement of the electrical conductivity on paste was coupled to isothermal calorimetry and BET measurements to get new insi...
Für die Herstellung von Betonfahrbahndecken ist für Ober- und Unterbeton ein Zement der gleichen Art und Festigkeitsklasse zu verwenden. Durch eine flexiblere Handhabung von Bindemitteln im Ober- und Unterbeton können sich ökologische und wirtschaftliche
Vorteile eröffnen. Ein sinnvoller Ansatz ist die Verwendung von Zementen mit hohem Klinkerantei...
Power Ultrasound (PUS) is widely used in various technical processes (from pharmaceutic to ceramic and fuel industry) to disperse suspensions and to control crystallization processes. Previous investigations by the authors have shown that a short PUS treatment during mixing process effectively accelerates the growth of strength determining C-S-H ph...
Short overview on three "recent" models for salt frost scaling.
For decades, electron microscopy has been a major analytical technique for the characterization of cementitious materials. During the last twenty years, new developments in scanning electron microscopy (SEM) have significantly improved the resolution of imaging and analytical possibilities. The current contribution aims to give an overview of the l...
Testing the resistance of concrete to frost and salt frost attack is a high-profile research subject because of the mass usage of this construction material. The corresponding test methods are regulated in relevant standards. Mortars are used in significantly smaller quantities and also only a certain proportion of these material mixes requires a h...
In kalten oder gemäßigten Klimata können Außenbauteile aus Beton wiederholten Frost-Tauwechseln bei gleichzeitiger Feuchtezufuhr ausgesetzt sein. In Verbindung mit Tausalzen treten vorrangig Abwitterungen von der Betonoberfläche auf. Für die dafür zu Grunde liegenden Mechanismen existieren verschiedene Schadensmodelle, z.B. das thermodynamische Mod...
The hydration of two batches of tricalcium silicate was followed by isothermal heat conduction calorimetry and analysis of pore solution composition. These two samples were different in Al2O3-content and free lime concentration. It was observed that the material containing aluminum reacts slower than the pure one. The reactivity was also analyzed i...
Alkali-Silica Reaction (ASR) is a frequent cause of reduced concrete durability. Eliminating the application of alkali reactive aggregates would reduce the quantity of ASR concrete deterioration in the field. This study introduces an Electron Backscatter Diffraction (EBSD) technique to distinguish the ASR risk of slow-late reacting aggregates by me...
In concrete elements, simultaneously subjected to cyclic loadings and external alkalis, the risk for damage caused by or under participation of an alkali-silica reaction (ASR) is particularly high. This is of particular concern for concrete pavements due to the increasing heavy vehicle traffic and the application of sodium chloride (NaCl) de-icer d...
Die Eignung hüttensandhaltiger Zemente sowie von Steinkohlenflugaschen zur Vermeidung einer betonschädigenden Alkali‐Kieselsäure‐Reaktion (AKR) im Beton ist hinreichend bekannt. Im deutschen Betonstraßenbau werden entsprechende Bindemittel jedoch nur selten eingesetzt, da eine Verschlechterung des Frost‐Tausalz‐Widerstands des Betons erwartet wird,...
In this paper, the effects of curing temperature on the hydration of calcium aluminate cement (CAC) dominated ternary binders (studied CAC: Portland cement: calcium sulfate mass ratio were 22.5: 51.7: 25.8) were estimated at 0, 10, 20 and 40°C, respectively. Both α-hemihydrate and natural anhydrite were employed as the main source of sulfate. The i...
Improving concrete sustainability by increasing durability requires a detailed knowledge about microstructural properties. Due to the nanoscale nature of hydrate phases that determine concrete properties, microstructural characterization remains a challenge. Analytical electron microscopy offers promising techniques to characterize cement hydrates....
In this study the hydration kinetics and the development of concentrations in the pore solution of cement pastes containing different supplementary cementitious materials (blast-furnace slag, Si-rich fly ash, limestone, quartz) at a cement replacement of 50 wt.% were investigated during the first 6 h of hydration. The results indicate that the degr...
The effect of curing temperature on the early hydration of calcium aluminate cement-Portland cement-anhydrite ternary blends was determined by calorimetry, X-ray diffraction, environmental scanning electronic microscopy (backscattered electron imaging) and mercury intrusion porosimetry, respectively. The related phase composition, microstructure of...
Modern tunnel engineering is nearly impossible without the usage of sprayed concrete. The most important property of sprayed concrete is the sudden and reliable setting and fast hardening after the addition of setting accelerator. At a recent construction project, the early strength development of sprayed concrete with an accelerator based on alumi...
At elevated concrete temperatures the placing and finishing of concrete is more difficult due to a faster rate of setting and hardening. The use of set retarders or retarding concrete plasticizers could delay the setting rate of the concrete, without necessarily impairing the quality of the pavement. For the production of concrete pavements with ex...
Study on the variable use of cements in two-lift concrete pavements with the aim to reduce the carbon footprint of concrete and to allow the application of a wider range of aggregates.
Characterization of native cement hydrates is one of the main challenges towards a complete understanding of hydration processes. Analytical electron microscopy is one of the promising methods to identify cement hydrates by using imaging, spectroscopic and diffraction information. In the present study results of high resolution Scanning Electron Mi...
The influence of rice husk ash (RHA, 20% and 40%, mass fraction) on the early hydration (hydration heat, hydration degree) of calcium aluminate cement was investigated by calorimetry, differential thermal-thermogravimetry and scanning electron microscopy, respectively. The results indicate that compared to other samples, the substitution of 20% RHA...
Ashes from lignite combustion for power generation contain strategic metals, metalloids and rare earth elements (REE) and may thus be a potential source of industrially demanded metals. The presented project focused on the assessment and utilization of this potential raw material. Lignite ash assessment showed that the largest ash amounts for a pot...
Gemäß dem Regelwerk für Betonstraßen muss für zweischichtige Betonfahrbahndecken derselbe Zement in Ober- und Unterbeton verwendet werden. Weiterhin ist die Anrechnung von Flugasche auf den w/z-Wert nicht gestattet. Durch eine flexiblere Handhabung der Bindemittel könnten sich Vorteile für die Betonbauweise ergeben. So könnte z.B. der stärker durch...
Interaction between cement composition and accelerator on performance of sprayed concrete.
Sorting analyses of construction and demolition wastes confirm a high heterogeneity of the recycling materials. The target is to separate impurities from the waste flow and subsequently separate different material fractions. The main focus is on the separation of gypsum attachments and composite particles, which cannot be avoided during mechanical...
The present study aims investigating the effects of superplasticizer (SP) and of mineral admixtures on self-compactability and compressive strength of mortar and of self-compacting high performance concrete (SCHPC). The results show that SP dosages higher than the SP saturation dosage (SSD) did not influence flowability and plastic viscosity, and i...
Im Rahmen des Bewerbungsverfahrens der Materialprüfungsanstalt Universität Stuttgart (MPA Universität Stuttgart) als zugelassener AKR‐Gutachter nach ARS 04/2013 [ 1 ] wurde ein breit angelegtes Untersuchungsprogramm an der MPA in Stuttgart und am Finger‐Institut (FIB) in Weimar durchgeführt. Im ersten Teil war es zunächst anhand von Vergleichsversu...
Abstract Superplasticizers are added to fresh concretes in order to improve workability. The interaction of superplasticizers with cement during hydration is not fully understood. It is investigated if the measured effects are principally related to the polymer structure and must therefore be considered in discussions. By means of titration experim...
In the present study, the resistance of mortar formulated from self-compacting high performance concrete containing rice husk ash (RHA)/silica fume (SF) and reactive/non-reactive aggregates to alkali silica reaction (ASR) was assessed.
For the mortar containing greywacke reactive aggregate, SF is significantly more effective than RHA in reducing ex...
The hydration of triclinic tricalcium silicate containing foreign oxides was investigated in this study. Two water/solid-ratios of 50 and 0.50 were applied. The kinetics of the reaction was analyzed by a combination of methods including thermal analysis, pore solution analysis, and calorimetry. From these data, the evolution of the rate of reaction...
This paper aims to review the progress in cement clinker chemistry since the last International Conference on the Chemistry of Cement in 2011. Although Portland cement clinker is still, by far, the most important compound of modern cements we show that there is a strong development of alternatives. This is mainly due to the emission of carbon dioxi...
This paper presents the results of several investigations concerning the durability of mortar and concrete with higher proportion of calcined clays in the cement part. For this purpose, different clays based on kaolinite, montmorillonite and illite were fired at optimum temperatures according to the strength contribution in cement. The raw material...
This paper is an effort towards presenting a new mix design method for self-compacting high performance concrete (SCHPC) containing various mineral admixtures (MA). In the proposed method, the constituent materials were calculated by using the absolute volume method. The packing theory of Funk and Dinger with the exponent q = 0.25 was adopted to de...